SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '624bfcef54c57e5e4ae3d11d241b611085f4134549d8d060295194b0543b9f1b' 
  AND token = 'VgVx43YvDhSXKpLO08kYOMpu3atwAtObzaGtifS9U3g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}